Apple pomace biorefinery for ethanol, mycoprotein, and value-added biochemicals production by Mucor indicus

Abstract

Apple pomace, a waste resulting after juice extraction, is often discarded in landfills, which can cause environmental issues. However, since apple pomace contains high levels of free sugars and structural carbohydrates, its conversion to fuels and biomaterials can mitigate environmental issues. In this study, an apple pomace feedstock-based biorefinery utilizing ethanolic Organosolv pretreatment and simultaneous saccharification and fermentation (SSF) was conceptualized. Ethanolic based Organosolv pretreatment was performed at 24 different conditions to find the optimum conditions for maximum ethanol production. The resulting pretreated solids and pretreatment liquor were fermented to ethanol and/or biomass with filamentous fungi Mucor indicus. The pretreatment of apple pomace at 100 °C for 30 min with 50% ethanol and 0.5% sulfuric acid resulted in the highest ethanol yield of 244.9 g/kg of apple pomace. This yield included 47.2 g ethanol from pretreated solids and 197.7 g from pretreatment liquor, where the corresponding amount of pretreatment liquor and solids were subjected to fermentation. However, the aerobic fermentation of pretreatment liquor resulted in lower ethanol yield (117.4 g/kg of apple pomace) than the fermentation under anaerobic conditions, but high levels of mycoprotein (29.0 g/kg of apple pomace) and chitin and chitosan (8.7 g/kg of apple pomace) were produced.